Sterling refrigerating system and cooling device

ABSTRACT

A ring-shaped jacket is fitted around the warm section of a Stirling refrigerating device, and a cylindrical heat-rejecting heat exchanger is disposed around the body of the Stirling refrigerating device with a gap secured in between. The jacket and the heat-rejecting heat exchanger are connected together with a pipe to form a closed circuit, and a refrigerant is circulated through the closed circuit. This allows the heat in the warm section to be transferred by the refrigerant, permitting efficient heat rejection from the heat-rejecting heat exchanger. Thus, the desired cold is obtained stably from the cold section of the Stirling refrigerating device.

TECHNICAL FIELD

[0001] The present invention relates to a refrigerating system providedwith a Stirling refrigerating device, and to a cooling apparatus such asa refrigerator employing such a refrigerating system.

BACKGROUND ART

[0002] In general, refrigerating cycle apparatuses such as householdrefrigerators adopt a vapor compression refrigerating cycle using a CFC(chlorofluorocarbon) as a refrigerant. As is well known, however, CFCsare notorious for their material contribution to the destruction of theozone layer and, from the perspective of saving the environment, theiruse is increasingly restricted worldwide.

[0003] In recent years, as new refrigerating technology to replace thevapor compressing refrigerating cycle, much research has been done onStirling refrigerating devices exploiting the reversed Stirling cycle. AStirling refrigerating device uses an inert gas such as helium as aworking medium, and therefore provides a cryogenic temperatureefficiently without adversely affecting the global environment.

[0004] The reversed Stirling cycle is a closed cycle in which heatrejection and heat absorption are performed by repeatedly compressingand expanding a working medium together with a displacer driven toreciprocate with a predetermined phase difference kept relative to apiston inside a single cylinder by driving the cylinder with an externalforce fed from a linear motor or the like.

[0005] A Stirling refrigerating device requires a means for efficientlytransferring the cold obtained in a low-temperature portion, called thecold section, thereof Moreover, the higher the refrigeration performanceof the Stirling refrigerating device, the larger the amount of heatgenerated in a heat-rejection portion, called the warm section, thereof,and therefore, unless the generated heat is efficiently rejected, theStirling refrigerating device shows poor refrigeration performance,producing less cold than expected in its cold section.

[0006] For example, in the Stirling refrigerator disclosed in JapanesePatent Application Laid-Open No. H7-180921, as shown in FIG. 20, acooler 101 for cooling the interior of the refrigerator is arranged in ahighest, deepest position inside the body 100 of the refrigerator, and aStirling refrigerating device 102 is housed inside a machine compartmentat the bottom of the body. The cold section 103 of the Stirlingrefrigerating device 102 is connected to the cooler 101 by way of a pipe104 filled with a working medium, and the working medium is circulatedso that, when the Stirling refrigerating device 102 is operated, thecold generated in the cold section 103 is transferred by the workingmedium to the cooler 101 placed inside the refrigerator.

[0007] Then, the cold air obtained through heat exchange taking place onthe surface of the cooler 101 between the cold transferred to the cooler101 and the air inside the refrigerator is blown into the refrigeratorinterior by a fan 105, so that the refrigerator interior is cooled to apredetermined temperature. On the other hand, in the warm section 106 ofthe Stirling refrigerating device 102, heat-rejecting fins 107 arearranged, and air is blown therethrough by a blower fan 108 to promptheat rejection from the warm section 106.

[0008] However, while refrigeration performance of the order of a fewhundred watts is required in Stirling refrigerators for which highdemands are expected as models for household and commercial use,attempting to achieve such refrigeration performance with theconventional construction described above results in extremelyincreasing the surface area of the heat-rejecting fins 10 and theamounts of cooling air blown by the blower fan 108.

[0009] This makes the refrigerating system as a whole larger, and thusmakes it necessary to secure, for the machine compartment, a volume aslarge as or larger than in a conventional refrigerator of the vaporcompression type. This not only makes it inevitable to reduce the volumeof the remaining space inside the refrigerator, but also, as a result ofincreased electric power consumption by the fan, degrades the efficiencyof the system as a whole, contrary to energy saving.

DISCLOSURE OF THE INVENTION

[0010] An object of the present invention is to provide a compactStirling refrigerating system with enhanced refrigeration efficiencyachieved by prompting heat rejection from the warm section.

[0011] To achieve the above object, according to one aspect of thepresent invention, a Stirling refrigerating system is provided with: aStirling refrigerating device including a piston and a displacer thatreciprocate with a predetermined phase difference kept therebetweeninside a cylinder having a working medium sealed therein, a heatabsorber that absorbs heat from outside to produce cold as a result ofthe working medium being expanded in an expansion space formed insidethe cylinder as the displacer reciprocates, and a heat rejecter thatrejects, to outside, heat generated as a result of the working mediumbeing compressed in a compression space formed inside the cylinder asthe piston reciprocates; a ring-shaped member fitted to the heatrejecter and having a refrigerant flow passage; a cylindricalheat-rejecting heat exchanger disposed around the Stirling refrigeratingdevice with a gap secured in between and formed so as to have arefrigerant flow passage; a refrigerant circulation passage formed byconnecting the refrigerant flow passage of the ring-shaped member andthe refrigerant flow passage of the heat-rejecting heat exchanger with apipe; and circulating means for circulating a refrigerant through therefrigerant circulation passage.

[0012] Specifically, the heat-rejecting heat exchanger is composed of afirst header pipe having at one end thereof a connection port to whichone end of the pipe is connected, a second header pipe laid next to thefirst header pipe and parallel, together with the first header pipe, tothe axis of the Stirling refrigerating device and having at one endthereof a connection port to which the other end of the pipe isconnected, a plurality of ring-shaped condenser pipes that connect thefirst and second header pipes together so that they communicate witheach other therethrough, and fins fitted between the plurality ofcondenser pipes. In this construction, the refrigerant that hascollected compression heat in the compression space flows through thepipe into the second header pipe, and then flows through the ring-shapedcondenser pipes into the first header pipe. Meanwhile, the compressionheat is transferred to the fins, and is efficiently rejected from thesurfaces of the fins. In this case, the condenser pipes and the fins maybe given substantially equal lengths in the radial directions of theStirling refrigerating device. This helps increase the surface area ofthe fins that contributes to heat rejection.

[0013] On the other hand, the transferring means comprises a cylindricalrod slide portion formed at the end of the Stirling refrigerating deviceopposite to the heat absorber, a rod slidable together with the pistonalong the inner surface of the rod slide portion, a first magnet fittedat the tip end of the rod, a box member fitted at the tip end of the rodslide portion and forming part of the refrigerant circulation passage, aresonant spring placed inside the box member and having the rod slideportion placed therethrough, a second magnet slidable along the outersurface of the rod slide portion by the action of the resonant spring,and a movable member fixed to the second spring and capable ofreciprocating along the outer surface of the rod slide portion and alongthe inner surface of the box member. The refrigerant that has flowedinto the box member is discharged out of it by the pumping action ofreciprocating movement of the movable member.

[0014] In this construction, as the piston reciprocates, the firstmagnet fitted at the tip end of the rod reciprocates together, and, bythe magnetism it exerts, the second magnet also reciprocates along theouter surface of the rod slide portion. Thus, the refrigerant that flowsinto the box member is discharged out of it by the doughnut-shapedmember. This eliminates the need to use as a transferring means anexternal force as provided by a circulating pump or the like, and thushelps save energy.

[0015] A blower fan that blows air through the space inside theheat-rejecting heat exchanger may be provided. The air blown by theblower fan then prompts heat rejection from the surfaces of the fins ofthe heat-rejecting heat exchanger.

[0016] In this case, the fins may be so formed as to protrude outwardfrom the outer profile of the condenser pipes in the radial directions.This increases, on the downstream side of the blown air, the surfacearea of the fins that contributes to heat rejection, and thus helpsfurther prompt heat rejection from the fins by the blown air.

[0017] Another example of the heat-rejecting heat exchanger comprises afirst header pipe having at both ends thereof connection ports that areconnected to the pipe and having an internal space thereof partitionedoff in a length direction thereof, a second header pipe laid next to thefirst header pipe and parallel, together with the first header pipe, tothe axis of the Stirling refrigerating device, a plurality ofring-shaped condenser pipes that connect the first and second headerpipes together so that they communicate with each other therethrough,and fins fitted between the plurality of condenser pipes.

[0018] In this construction, the refrigerant that has collectedcompression heat in the compression space flows through the pipe intothe first header pipe, and then flows through the ring-shaped condenserpipes located on the upstream side of the partition plate into thesecond header pipe. Moreover, the refrigerant filling the second headerpipe flows through the ring-shaped condenser pipes located on thedownstream side of the partition plate back into the first header pipe.Meanwhile, the compression heat is transferred to the fins, and isefficiently rejected form the surfaces of the fins.

[0019] To achieve the above object, according to another aspect of thepresent invention, a Stirling refrigerating system is provided with: aStirling refrigerating device including a piston and a displacer thatreciprocate with a predetermined phase difference kept therebetweeninside a cylinder having a working medium sealed therein, a heatabsorber that absorbs heat from outside to produce cold as a result ofthe working medium being expanded in an expansion space formed insidethe cylinder as the displacer reciprocates, and a heat rejecter formedas a ring-shaped refrigerant flow passage that rejects, to arefrigerant, heat generated as a result of the working medium beingcompressed in a compression space formed inside the cylinder as thepiston reciprocates; a heat-rejecting heat exchanger disposed around theStirling refrigerating device with a gap secured in between and formedso as to have a refrigerant flow passage; a refrigerant circulationpassage formed by connecting the refrigerant flow passage of the heatrejecter and the refrigerant flow passage of the heat-rejecting heatexchanger with a pipe; and circulating means for circulating arefrigerant through the refrigerant circulation passage.

[0020] In a cooling apparatus having a Stirling refrigerating system asdescribed above housed inside a machine compartment formed at the bottomof the body of the cooling apparatus, the interior of the body, enclosedwith a heat-insulating material, is cooled by exploiting cold generatedin the heat absorber as the Stirling refrigerating device is operated.

BRIEF DESCRIPTION OF DRAWINGS

[0021]FIG. 1 is a sectional view of an example of a free-piston-typeStirling refrigerating device.

[0022]FIG. 2 is a partially cutaway side view showing an outline of theconstruction of the Stirling refrigerating system of a first embodimentof the invention.

[0023]FIG. 3 is an enlarged sectional view showing the structure of thejacket of the Stirling refrigerating system.

[0024]FIG. 4A is a top view showing the construction of theheat-rejecting heat exchanger of the Stirling refrigerating system.

[0025]FIG. 4B is a side view showing the construction of theheat-rejecting heat exchanger of the Stirling refrigerating system.

[0026]FIG. 5 is a sectional view of the condenser pips of theheat-rejecting heat exchanger.

[0027]FIG. 6 is a diagram schematically showing the structure of aprincipal portion of the heat-rejecting heat exchanger.

[0028]FIG. 7 is a partially cutaway external view showing an outline ofthe construction of the Stirling refrigerating system of a secondembodiment of the invention.

[0029]FIG. 8 is an enlarged sectional view showing a portion of theStirling refrigerating system.

[0030]FIG. 9 is a partially cutaway side view showing an outline of theconstruction of the Stirling refrigerating system of a third embodimentof the invention.

[0031]FIG. 10 is a graph showing the relationship between the volume ofair blown by the lower fan and the heat exchange performance of theheat-rejecting heat exchanger in the Stirling refrigerating system.

[0032]FIG. 11 is a sectional view showing the structure of the jacket ofthe Stirling refrigerating system of a fourth embodiment of theinvention.

[0033]FIG. 12 is a side view showing the construction of theheat-rejecting heat exchanger of the Stirling refrigerating system of afifth embodiment of the invention.

[0034]FIG. 13 is an enlarged sectional view of a portion of theheat-rejecting heat exchanger.

[0035]FIG. 14 is graph showing the relationship between the volume ofair blown by the lower fan and the heat exchange performance of theheat-rejecting heat exchanger in the Stirling refrigerating system, withvarying fin widths.

[0036]FIG. 15 is a sectional view schematically showing the constructionof the heat-rejecting heat exchanger of the Stirling refrigeratingsystem of a sixth embodiment of the invention.

[0037]FIG. 16 is an enlarged sectional view of a portion of the Stirlingrefrigerating system of a seventh embodiment of the invention.

[0038]FIG. 17 is an external perspective view showing an outline of theconstruction of the refrigerator of an eighth embodiment of theinvention.

[0039]FIG. 18 is a perspective view of the machine compartment unit ofthe refrigerator.

[0040]FIG. 19 is a perspective view of the cooler of the refrigerator.

[0041]FIG. 20 is a side sectional view showing an outline of an exampleof the construction of a conventional Stirling refrigerator.

BEST MODE FOR CARRYING OUT THE INVENTION

[0042] Hereinafter, embodiments of the present invention will bedescribed with reference to the drawings.

[0043] A first embodiment of the invention will be described below withreference to the drawings. FIG. 1 is a sectional view of afree-piston-type Stirling refrigerating device. First, how thisrefrigerating device operates will be described.

[0044] A piston 2 is driven by a linear motor 6, and moves sinusoidallyby the action of a resonant spring 5. As the piston, 2 reciprocates,working gas in an expansion space 8 exhibits sinusoidal pressurefluctuation. This pressure fluctuation of the working gas is convertedinto a force that drives a displacer 1 provided inside a cylinder 9 a tomove axially. Thus, the displacer 1, by the action of a resonant spring51, moves sinusoidally with a predetermined phase difference (forexample, 90°) kept relative to the piston 2.

[0045] The working gas compressed in the expansion space 8 rejectscompression heat in a warm section (heat rejecter) 10, is then precooledby a regenerator 3 provided inside the displacer 1, and then flows intoan expansion space 7. On the other hand, the working gas in theexpansion space 7 is expanded by the movement of the displacer 1, andabsorbs heat from outside through a cold section (heat absorber) 4provided at the tip end of a Stirling refrigerating device body 9. Thus,cryogenic cold is obtained in this cold section 4.

[0046]FIG. 2 is a sectional view showing an outline of the configurationof the Stirling refrigerating system 32 of this embodiment. FIG. 2 showsa case in which the Stirling refrigerating device body 9 is disposedhorizontally with the cold section 4 at the left. Around a cylindricalportion of the Stirling refrigerating device body 9 from about theright-hand end thereof to about the right-hand end of the warm section10, there is provided a cylindrical heat-rejecting heat exchanger 11with a gap secured from the circumference of the Stirling refrigeratingdevice 9. In the figure, for easy understanding of the construction ofthe heat-rejecting heat exchanger 11, the upper half thereof, locatedabove the Stirling refrigerating device body 9, is partially cut away.

[0047] Around the warm section 10 is fitted a ring-shaped jacket 12. Thejacket 12 is ring-shaped, and has a doughnut-shaped space 41 formedinside. As shown in FIG. 3, the jacket 12 is composed of a C-shaped ring12 a and a flat plate 12 b that hermetically closes the open side of thering 12 a. In two opposite places on the jacket 12 across the centerthereof, there are provided a first and a second connection port 13 aand 13 b to which pipes 14 are connected.

[0048] As shown in a top view and a side view in FIGS. 4A and 4B, theheat-rejecting heat exchanger 11 is composed of a first header pipe 191and a second header pipe 192 arranged next to each other and parallel tothe axis of the Stirling refrigerating device body 9 with theirconnection ports 191 a and 192 a pointing in opposite directions, aplurality of ring-shaped condenser pipes 17 that connect the first andsecond header pipes 191 and 192 together at predetermined intervals sothat they communicate with each other, and corrugated fins 18 fittedbetween the condenser pipes 17.

[0049] Now, the procedure for producing the heat-rejecting heatexchanger 11 will be described. First, the first and second header pipes191 and 192 are arranged on a plane, parallel to but away from eachother. Then, the plurality of condenser pipes 17 are fitted into thefirst and second header pipes 191 and 192 in places thereon facing eachother, and are held with a jig to maintain a predetermined shape. Then,the fins 18 are fitted between the condenser pipes 17 to produce a flatprototype of the heat-rejecting heat exchanger 11. Then, theheat-rejecting heat exchanger 11 is heated inside a blast furnace set atabout 620° C. so that its components are welded together where they fitinto or make contact with one another. Then, the heat-rejecting heatexchanger 11 is taken out of the blast furnace and cooled, and then thecondenser pipes 17 are bent along the circumferential surface of acylindrical jig so that the heat-rejecting heat exchanger 11 is formedinto a ring-like shape with the first and second header pipes 191 and192 placed next to each other. Then, the connection ports 191 a and 192a are fitted respectively at one end of each of the first and secondheader pipes 191 and 192. Lastly, the first and second header pipes 191and 192 are fixed to each other with a spacer 20, made of a materialwith low thermal conductivity, such as a resin, interposed in between tocomplete the heat-rejecting heat exchanger 11, now cylindrical.

[0050] One role of the spacer 20 is to maintain the ring-like shape byacting against the force exerted by the condenser pipes 17, which havebeen bent along the jig, to restore their original shape. Another roleof the spacer 20 is to separate the first and second header pipes 191and 192 from each other with a material with low thermal conductivity sothat no heat exchange takes place as the refrigerant enters the secondheader pipe 192, circulates through the condenser pipes 17, and exitsfrom the first header pipe 191. The spacer 20 also serves as a fittingleg that is fixed to the bottom surface of the machine compartment orthe like of the refrigerator. The first and second header pipes 191 and192 themselves do not make direct contact with the fins 18, and thusform a dead space that contributes little to heat exchange. However, byarranging the heat-rejecting heat exchanger 11 with the first and secondheader pipes 191 and 192 down, it is possible to permit the fins 18 toface a wide space and thereby enhance heat exchange efficiency.

[0051]FIG. 5 shows the sectional structure of the condenser pipes 17,taken along line x-x shown in FIG. 4A. As shown in FIG. 5, the condenserpipes 17 are flat pipes each having multiple channels, and have theirinterior formed into a triangular truss structure with reinforcementribs. These condenser pipes 17 are easily formed by extrusion molding ofaluminum. In FIG. 5, W represents the length of the condenser pipes 17in the radial directions of the Stirling refrigerating device body 9,and T represents their thickness.

[0052] As shown in FIG. 6, the fins 18 fitted between the condenserpipes 17 are each formed by bending thin aluminum foil at regularintervals into a corrugated shape, and are arranged parallel to oneanother to form a ring-like shape. The condenser pipes 17 and the fins18 are given substantially equal lengths in the radial directions of theStirling refrigerating device body 9.

[0053] Moreover, as shown in FIG. 2, pipes 14 are connected between theconnection port 191 a of the first header pipe 191 and the firstconnection port 13 a of the jacket 12, between the second connectionport 13 b of the jacket 12 and a circulation pump 15, and between thecirculation pump 15 and the connection port 192 a of the second headerpipe 192 to form a closed circuit. In this closed circuit is sealed afluid, such as ethyl alcohol, as a refrigerant 16. As the circulationpump 15 is operated, the refrigerant 16 is circulated in the directionindicated by arrows.

[0054] In FIG. 2, when the circulation pump 15 is operated, thecompression heat generated in the warm section 10 of the Stirlingrefrigerating device body 9 conducts through the jacket 12 to therefrigerant 16, and is then transferred through the pipes 14 to theheat-rejecting heat exchanger 11. As the refrigerant 16 passes throughthe condenser pipes 17, the heat is rejected from the surfaces of thefins 18 to outside.

[0055] In this embodiment, the jacket 12 is formed as a combination of aC-shaped ring 12 a and a flat plate 12 b. Instead, a flattened tube maybe wound around the warm section 10.

[0056] A second embodiment of the invention will be described below withreference to the drawings. FIG. 7 is a partially cut-away external viewshowing an outline of the configuration of the Stirling refrigeratingsystem of this embodiment, and FIG. 8 is an enlarged sectional view of aportion of the Stirling refrigerating system. In these figures, suchcomponents as are common to the first embodiment shown in FIG. 2 anddescribed above are identified with the same reference numerals, andtheir detailed explanations will not be repeated.

[0057] The characteristic features of this embodiment will be describedwith reference to FIGS. 7 and 8. At the right-hand end of the Stirlingrefrigerating device body 9, i.e., at the end thereof opposite to thecold section 4, there is disposed a cylindrical rod slide portion 9 b.Into the space inside this rod slide portion 9 b is inserted a rod 22that can slide axially along the inner surface thereof One end of therod 22 is fixed to the center of the piston 2 in the axial directionthereof, and the other end of the rod 22 is fitted with a first magnet23 a.

[0058] At the tip end of the rod slide portion 9 b is fitted acylindrical box member 24. Inside the box member 24, there are provideda resonant spring 52 through which the rod slide portion 9 b is placed,a second magnet 23 b that can slide along the outer surface of the rodslide portion 9 b, and a doughnut-shaped member 21 that is fixed to thesecond magnet 23 b and that can slide along the outer surface of the rodslide portion 9 b and along the inner surface of the box member 24. Thesecond magnet 23 b is fixed to the inner surface of the box member 24 bythe resonant spring 52. In an upper portion of the circumferentialsurface of the box member 24, and in the right-hand end surface thereof,a first and a second connection ports 24 a and 24 b are respectivelyformed.

[0059] Moreover, pipes 14 are connected between the connection port 191a of the first header pipe 191 and the first connection port 13 a of thejacket 12, between the second connection port 13 b of the jacket 12 andthe first connection port 24 a of the box member 24, and between thesecond connection port 24 b of the box member 24 and the connection port192 a of the second header pipe 192 to form a closed circuit.

[0060] In FIG. 8, when the linear motor 6 is operated, the piston 2reciprocates, and the rod 22, together with the first magnet 23 a,reciprocates with the same period as the piston 2. Simultaneously, thesecond magnet 23 b starts reciprocating so as to be resonant with thefirst magnet 23 a. That is, as the first magnet 23 a moves rightward,the second magnet 23 b moves rightward by the action of their magnetismattracting each other. Similarly, as the first magnet 23 a movesleftward, the second magnet 23 b moves leftward. The resonance amplitudeof the second magnet 23 b is set about equal to that of the first magnet23 a by the resonant spring 52. Together with the second magnet 23 b,the doughnut-shaped member 21 reciprocates leftward and rightward. As aresult, as indicated by arrows in FIG. 8, the refrigerant 16 that hasbrought into the box member 24 by a pumping mechanism is driven out ofit to circulate through the closed circuit connected by the pipes 14.

[0061] The linear motor 6 is generally operated at the frequency ofcommercially distributed electric power (50 or 60 Hz). Accordingly, thepiston 2 reciprocates at that frequency, and the doughnut-shaped member21 inside the box member 24 reciprocates at the same frequency. Thispermits the refrigerant 16 to be transferred with satisfactoryperformance. In a case where the Stirling refrigerating device is of acrank type, the rotational movement of the motor that drives the pistonand the displacer may be exploited to rotate an impeller provided insidethe box member and thereby achieve a similar pumping mechanism.

[0062] A third embodiment of the invention will be described below withreference to the drawings. FIG. 9 is a partially cut-away side viewshowing an outline of the construction of the Stirling refrigeratingsystem of this embodiment. In this figure, such components as arecomment to the first embodiment shown in FIG. 2 and described earlierare identified with the same reference numerals, and their detailedexplanations will not be repeated.

[0063] The characteristic features of this embodiment will be describedwith reference to FIG. 9. On the right-hand side of the heat-rejectingheat exchanger 11, i.e., on the side opposite to the cold section 4,there is disposed a blower fan 25 that can rotate about the axis of theStirling refrigerating device body 9. On the other hand, on theright-hand side of the heat-rejecting heat exchanger 11, a ring-shapedshielding plate 26 is fitted around the warm section 12, next to thejacket 12. The shielding plate 26 has a diameter at least greater thanthat of the heat-rejecting heat exchanger 11, and serves to shield theair 27 blown into the heat-rejecting heat exchanger 11 as the blower fan25 rotates so that it does not leak to the warm section 10.

[0064] The air 27 blown as the blower fan 25 rotates flows inside theheat-rejecting heat exchanger 11 along the Stirling refrigerating devicebody 9, is then shielded by the shielding plate 26, and then passesbetween the fins 18 so as to be discharged out of the heat-rejectingheat exchanger 11. This prompts heat rejection by the heat-rejectingheat exchanger 11. In this case, as shown in FIG. 10, the heat exchangeperformance of the heat-rejecting heat exchanger 11 can be controlled byincreasing or decreasing the volume of air blown by the blower fan 25.

[0065] As described earlier, the Stirling refrigerating device is adevice in which the piston 2 is driven by the linear motor 6 to producea cold temperature in the cold section 4. This means that, by varyingthe rms value of the alternating-current voltage applied to the linearmotor 6, it is possible to vary the amplitude of the reciprocatingmovement of the piston 2. In fact, as the rms value of thealternating-current voltage applied to the linear motor 6 is increasedas time passes, the amplitude of the piston 2 increases accordingly, andthe pressure of the working gas compressed in the expansion space 8gradually increases. As a result, the amount of heat absorbed when theworking gas is expanded by the displacer 1 in the expansion space 7increases. This permits a lower temperature to be produced in the coldsection 4.

[0066] However, as the pressure of the working gas in the expansionspace 8 increases, the compression heat generated in the warm section 10increases. Thus, unless the increased compression heat is efficientlyrejected, the refrigeration performance of the Stirling lowers, and thetemperature of the cold section 4 rises.

[0067] When the Stirling refrigerating device is being operated at anextremely low output, it is sufficient to operate the circulation pump15 alone without rotating the blower fan 25 so that the heat in the warmsection 10 is transferred to the heat-rejecting heat exchanger 11 by therefrigerant 16 and rejected naturally. However, as the output of theStirling refrigerating device increases, the blower fan 25 needs to beenergized to increase the heat exchange performance of theheat-rejecting heat exchanger 11.

[0068] As described above, the refrigeration performance of the Stirlingrefrigerating device is largely proportional to the rms value of thealternating-current voltage applied to the linear motor 6. Therefore,the input to the blower fan 25 is controlled according to the input tothe linear motor 6. Specifically, when the input to the linear motor 6is increased, the input to the blower fan 25 is increased and, when theinput to the linear motor 6 is decreased, the input to the blower fan 25is decreased. In particular, when the Stirling refrigerating device isoperated at its maximum output, the input to the circulation pump 15 isincreased to increase the circulation of the refrigerant and the inputto the blower fan 25 is increased to increase the volume of blown air tomaximize rejection of the compression heat generated in the warm section10.

[0069] In this embodiment, the air 27 blown as the blower fan 25 rotatesflows inside the heat-rejecting heat exchanger 11 along the Stirlingrefrigerating device body 9, and then passes between the fins 18 so asto be discharged to outside. However, the same effect is achieved bypassing air in the reverse direction, specifically by sucking air infrom outside the heat-rejecting heat exchanger 11 and then passing italong the Stirling refrigerating device body 9 so as to discharge it tobehind the blower fan 25.

[0070] A fourth embodiment of the invention will be described below withreference to the drawings. FIG. 11 is a sectional view showing thestructure of the jacket of the Stirling refrigerating system of thisembodiment. The characteristic feature of this embodiment is that, asshown in FIG. 11, inside the jacket 12 fitted around the warm section10, fins 28 are arranged in a ring-like shape. These fins 28, like thefins 18 of the heat-rejecting heat exchanger 11, are corrugated bybending thin copper foil at regular intervals by the use of a gear.

[0071] The fins 28 are welded to the interior of the jacket 12 allaround the space inside it so that their bent portions are kept incontact with the inner and outer walls of the interior of the jacket 12.The first and second connection ports 13 a and 13 b of the jacket 12 areprovided in the flow path of the refrigerant so as to face each other onthe upstream and downstream sides of the fins 28. This permits therefrigerant 16 passing inside the jacket 12 to make contact with a widearea on the surfaces of the fins 28.

[0072] Next, the flow of the refrigerant will be described withreference to FIG. 11. As the circulation pump 15 (see FIG. 2) isoperated, the refrigerant 16 flows through the pipe 14 into the jacket12 via the first connection port 13 a. The refrigerant 16 inside thejacket 12 fills, owing to the pressure loss through the fins 28, theupstream side (right-hand side) portion thereof, and then passes throughthe fins 28 to move to the downstream side (left-hand side) portionthereof. Thereafter, the refrigerant 16 exits via the second connectionport 13 b and is transferred through the pipe 14 to the heat-rejectingheat exchanger 11 (see FIG. 2). This permits the heat of the warmsection 10 to be transferred effectively to the refrigerant 16 and thushelps enhance heat exchange efficiency.

[0073] Incidentally, narrowing the pitch of the fins 18 (see FIG. 6) ofthe heat-rejecting heat exchanger 11 is considered to increase thesurface area that contributes to heat exchange and thus increase theheat exchange performance of the heat-rejecting heat exchanger 11.

[0074] In common household refrigerators, a mechanical component such asa Stirling refrigerating device is housed in a machine compartmentlocated at the bottom of the body. The machine compartment is usually sodesigned that outside air is allowed in for heat rejection. Therefore,the heat-rejecting heat exchanger 11, when the pitch of the fins 18 isnarrowed, tends to suffer from dust contained in outside air collectingbetween the fins 18, eventually resulting in lower heat exchangeefficiency. This being the case, how to enhance heat exchangeperformance without unduly reducing the pitch of the fins 18 will bedescribed below.

[0075] A fifth embodiment of the invention will be described below withreference to the drawings. FIG. 12 is a side view showing theconfiguration of the heat-rejecting heat exchanger of the Stirlingrefrigerating system of the fifth embodiment of the invention, and FIG.13 is an enlarged sectional view showing a portion of the heat-rejectingheat exchanger.

[0076] In this embodiment, as shown in FIGS. 12 and 13, the fins 18 areextended so as to protrude outward, by a distance of d, from the outerprofile of the condenser pipes 17 in the radial directions of theStirling refrigerating device body 9. Accordingly, the length of thefins 18 (hereinafter “the width of the fins 18”) in the radialdirections of the Stirling refrigerating device body 9 equals W+d.

[0077] As shown in FIG. 13, the air 27 blown as the blower fan 25 (seeFIG. 9) rotates passes between the fins 18 and is discharged from thespace A inside the heat-rejecting heat exchanger 11 to the space Boutside it. There is a slight temperature slope on the surfaces of thefins 18. Specifically, the temperature in entrance portions 18 a thereofwhere the flow speed is unstable is lower than in exit portions 18 bthereof where the flow of air 27 is substantially uniform. Therefore,the exit portions 18 b contribute more to heat exchange performance.

[0078]FIG. 14 shows an example of the relationship between the width ofthe fins 18 and the heat exchange performance of the heat-rejecting heatexchanger, with the symbol ♦ indicating a case where the fins 18 have awidth of W and the air 27 flows in the normal direction (from A to B inFIG. 13), the symbol ▴ indicating a case where the fins 18 have a widthof W+d and the air flows in the opposite direction (from B to A in FIG.13), and the symbol ▪ indicating a case where the fins 18 have a widthof W+d and the air flows in the normal direction. With the air 27flowing in the normal direction, by extending the fins 18, it waspossible to enhance heat exchange performance by about 20%. It was alsoconfirmed that, even with the air 27 flowing in the reverse direction,heat exchange performance increased modestly by about 8%.

[0079] Another way to enhance the heat exchange performance of theheat-rejecting heat exchanger 11 is to increase the number of condenserpipes 17 and increase the number of fins 18 fitted between the condenserpipes 17 so as to increase the surface area that contributes to heatexchange.

[0080] However, when the number of condenser pipes 17 is increased, themore condenser pipes 17 branch off the first and second header pipes 191and 192, the greater the pressure loss occurring in the refrigerant 16circulating therethrough tends to be. This may hinder the refrigerant 16that has flowed into the individual condenser pipes 17 from flowinguniformly therethrough, and thus eventually leads to lower heat exchangeefficiency.

[0081] A sixth embodiment of the invention will be described below withreference to the drawings. FIG. 15 is a schematic sectional view showingthe configuration of the heat-rejecting heat exchanger of the Stirlingrefrigerating system of this embodiment. It is to be noted that FIG. 15shows a two-dimensional section for easy understanding of theheat-rejecting heat exchanger 11 although, in reality, as shown in FIG.2, it has a cylindrical shape with the first and second header pipes 191and 192 arranged next to each other and parallel to the axis of theStirling refrigerating device body 9.

[0082] The characteristic features of this embodiment will be describedwith reference to FIG. 15. At both ends of the first header pipe 191,there are provided connection ports 191 a and 191 b that are connectedto the pipes 14. The second header pipe 192 is closed with no connectionport provided at either end. The first and second header pipes 191 and192 are connected together by 12 mutually parallel ring-shaped condenserpipes 17 so as to communicate with each other. At the center of thefirst header pipe 191 in its length direction, i.e., between the sixthand seventh condenser pipes 17, there is provided a partition plate 29for separating the interior of the first header pipe 191 into aleft-hand and a right-hand portion. This partition plate 29 is a diskmade of aluminum, the same material as the first header pipe 191.

[0083] The procedure for producing this heat-rejecting heat exchanger 11is basically the same as described earlier. At the center of the innersurface of the first header pipe 191, a groove is formed beforehand.Then, the partition plate 29 is inserted into the groove, and the firstand second header pipes 191 and 192 are arranged on a plane, parallel tobut away from each other. Then, the plurality of condenser pipes 17 arefitted into the first and second header pipes 191 and 192 in placesthereon facing each other, and are held with a jig to maintain apredetermined shape. Then, the fins 18 are fitted between the condenserpipes 17 to produce a flat prototype of the heat-rejecting heatexchanger 11. Then, the heat-rejecting heat exchanger 11 is heatedinside a blast furnace set at about 620° C. so that its components arewelded together where they fit into or make contact with one another.Then, the heat-rejecting heat exchanger 11 is taken out of the blastfurnace and cooled, and then the condenser pipes 17 are bent along thecircumferential surface of a cylindrical jig so that the heat-rejectingheat exchanger 11 is formed into a ring-like shape with the first andsecond header pipes 191 and 192 placed next to each other. Then, theconnection ports 191 a and 191 b are formed at both ends of the firstheader pipe 191. Lastly, the first and second header pipes 191 and 192are fixed to each other with a spacer 20 (see FIG. 4B), made of amaterial with low thermal conductivity, interposed in between tocomplete the heat-rejecting heat exchanger 11, now cylindrical.

[0084] Next, the flow of the refrigerant will be described. When thecirculation pump 15 is operated, the refrigerant 16 flows into the firstheader pipe 191 via the connection port 191 b, and then moves toward thepartition plate 29, filling the right-hand half of the first header pipe191. The refrigerant 16 then flows uniformly through the right-hand sixcondenser pipes 17 into the second header pipe 192. The refrigerant 16then moves leftward inside the second header pipe 192, and then flowsuniformly through the left-hand six condenser pipes 17. The refrigerant16 then flows through the first header pipe 191 and is then dischargedvia the connection port 191 a into the pipe 14.

[0085] In this embodiment, there are provided 12 condenser pipes 17.However, in a case where the Stirling refrigerating device yields higheroutput, and therefore the heat-rejecting heat exchanger 11 needs to beprovided with an increased number of condenser pipes 17, it is necessaryto increase the number of partition plates 29 that separate the interiorof the first header pipe 191 to permit the refrigerant 16 to flow backand forth an increased number of times so that the refrigerant 16 flowsuniformly through the individual condenser pipes 17.

[0086] A seventh embodiment of the invention will be described belowwith reference to the drawings. FIG. 16 is an enlarged sectional viewshowing a portion of the Stirling refrigerating system of thisembodiment. The characteristic features of this embodiment are that, asshown in FIG. 16, the warm section 10 is so formed as to have a C-shapedsection so that a doughnut-shaped space 41 is formed inside, and that aring-shaped internal heat exchanger 40 is provided so as to hermeticallyclose the inner side of the shaped-shaped space 41.

[0087] Next, the flow of the refrigerant will be described. When thecirculation pump 15 (see FIG. 2) is operated, the refrigerant 16 flowsinto the doughnut-shaped space 41 via the first connection port 13 a,then passes around the internal heat exchanger 40, and is thendischarged via the second connection port 13 b. This permits thecompression heat of the working gas to be efficiently transferred to therefrigerant 16 through the internal heat exchanger 40.

[0088] An eighth embodiment of the invention will be described belowwith reference to the drawings. FIG. 17 is an external perspective viewshowing an outline of the construction of a refrigerator taken up as anexample of a cooling apparatus incorporating a Stirling refrigeratingsystem. The refrigerator has an interior thereof formed inside a bodythereof by being enclosed with an insulating material, and therefrigerator interior is separated into a plurality of refrigeratorcompartments with partition plates.

[0089] In a lowest, deepest portion of the refrigerator body 30, amachine compartment unit 31 as shown in FIG. 18 is removably installedwith screws or the like. Inside the machine compartment unit 31, thereis housed a Stirling refrigerating system 32, which is a combination ofa Stirling refrigerating device body 9 of one of the first to seventhembodiments described above, a heat-rejecting heat exchanger 11, andother components, and in addition there are also housed a cold air duct33 that is connected via a cold air discharge opening 36 to a cold airpassage (not shown) formed in a deepest portion inside the refrigeratorbody 30 so as to communicate therewith, and an electric box 34 thatelectrically controls the various components of the refrigerator.

[0090] The cold section 4 of the Stirling refrigerating system 32 islocated inside the cold air duct 33, and the tip of the cold section 4is kept in intimate contact with a side surface of a cooler 35 havingthe shape of a rectangular parallelepiped which is also disposed insidethe cold air duct 33. Thus, the cold generated in the cold section 4 istransferred to the cooler 35 and stored therein.

[0091]FIG. 19 shows the structure of the cooler 35. Inside a frame openat the top and the bottom and having substantially the shape of arectangular parallelepiped, ribs are fitted to form a honeycombstructure. On the downstream side of the cooler 35 is arranged a blowerfan 38, and, as the blower fan 38 rotates, air flows from the bottom tothe top of the cooler 35 through the honeycomb structure inside thecooler 35 so that the cold stored in the cooler 35 is transferred fromthe surfaces of the ribs to the cold air.

[0092] The cold air is transferred, via the cold air discharge opening36 of the cold air duct 33 and through the cold air passage, into theinterior of the refrigerator body 30. The cold air circulates inside therefrigerator interior to cool it, and then returns, via a cool airreturn opening 37, to the upstream side of the cooler 35.

[0093] In this embodiment, the cold obtained from the Stirlingrefrigerating device is discharged, in the form of cold air, directlyinto the refrigerator interior to achieve cooling. However, it is alsopossible, as disclosed in Japanese Patent Application Laid-Open No.H7-180921, to perform heat exchange between a closed circuit throughwhich cold air is circulated and the air inside the refrigerator by wayof fins and blow the thus cooled air with a fan to achieve cooling. Thisembodiment deals with a refrigerator merely as one example of a coolingapparatus, and the Stirling refrigerating system described above may beremovably installed in any other type of cooling apparatus, for example,compact coolers and freezers.

[0094] Industrial Applicability

[0095] As described above, according to the present invention, a hollowring-shaped member is provided in a heat rejecter to which compressionheat is rejected as a Stirling refrigerating device is operated, and thering-shaped member is connected, with a pipe, to a cylindricalheat-rejecting heat exchanger fitted around the body of the Stirlingrefrigerating device to form a closed circuit, through which arefrigerant is circulated. This makes it possible to produce a Stirlingrefrigerating system in which the heat generated in a heat rejecter istransferred by a refrigerant so as to be efficiently rejected to outsideby a heat-rejecting heat exchanger. In this way, it is possible torealize a Stirling refrigerating system. This makes it possible toobtain the desired amount of cold stably from the heat absorber of theStirling refrigerating device.

[0096] This Stirling refrigerating system can be installed in aspace-saving manner inside a machine compartment formed at the bottom ofthe body of a cooling apparatus. Thus, by the use of the cold generatedin the heat absorber as the Stirling refrigerating device is operated,it is possible to efficiently cool the interior of the body enclosedwith an insulating material.

1. A Stirling refrigerating system comprising: a Stirling refrigeratingdevice including a piston and a displacer that reciprocate with apredetermined phase difference kept therebetween inside a cylinderhaving a working medium sealed therein, a heat absorber that absorbsheat from outside to produce cold as a result of the working mediumbeing expanded in an expansion space formed inside the cylinder as thedisplacer reciprocates, and a heat rejecter that rejects, to outside,heat generated as a result of the working medium being compressed in acompression space formed inside the cylinder as the piston reciprocates;a ring-shaped member fitted to the heat rejecter and having arefrigerant flow passage; a cylindrical heat-rejecting heat exchangerdisposed around the Stirling refrigerating device with a gap secured inbetween and formed so as to have a refrigerant flow passage; arefrigerant circulation passage formed by connecting the refrigerantflow passage of the ring-shaped member and the refrigerant flow passageof the heat-rejecting heat exchanger with a pipe; and circulating meansfor circulating a refrigerant through the refrigerant circulationpassage.
 2. A Stirling refrigerating system as claimed in claim 1,wherein the heat-rejecting heat exchanger comprises a first header pipehaving at one end thereof a connection port to which one end of the pipeis connected, a second header pipe laid next to the first header pipeand parallel, together with the first header pipe, to an axis of theStirling refrigerating device and having at one end thereof a connectionport to which another end of the pipe is connected, a plurality ofring-shaped condenser pipes that connect the first and second headerpipes together so that the first and second header pipes communicatewith each other therethrough, and fins fitted between the plurality ofcondenser pipes.
 3. A Stirling refrigerating system as claimed in claim2, wherein the condenser pipes and the fins have substantially equallengths in radial directions of the Stirling refrigerating device.
 4. AStirling refrigerating system as claimed in claim 1, wherein thecirculating means comprises a cylindrical rod slide portion formed at anend of the Stirling refrigerating device opposite to the heat absorber,a rod slidable together with the piston along an inner surface of therod slide portion, a first magnet fitted at a tip end of the rod, a boxmember fitted at a tip end of the rod slide portion and forming part ofthe refrigerant circulation passage, a resonant spring placed inside thebox member and having the rod slide portion placed therethrough, asecond magnet slidable along an outer surface of the rod slide portionby an action of the resonant spring, and a movable member fixed to thesecond spring and capable of reciprocating along the outer surface ofthe rod slide portion and along an inner surface of the box member, andthe refrigerant that has flowed into the box member is discharged outthereof by a pumping action of reciprocating movement of the movablemember.
 5. A Stirling refrigerating system as claimed in claim 2,wherein there is provided a blower fan that blows air through a spaceinside the heat-rejecting heat exchanger.
 6. A Stirling refrigeratingsystem as claimed in claim 5, wherein the fins protrude outward from anouter profile of the condenser pipes in radial directions of theStirling refrigerating device.
 7. A Stirling refrigerating system asclaimed in claim 1, wherein the heat-rejecting heat exchanger comprisesa first header pipe having at both ends thereof connection ports thatare connected to the pipe and having an internal space thereofpartitioned off in a length direction thereof, a second header pipe laidnext to the first header pipe and parallel, together with the firstheader pipe, to an axis of the Stirling refrigerating device, aplurality of ring-shaped condenser pipes that connect the first andsecond header pipes together so that the first and second header pipescommunicate with each other therethrough, and fins fitted between theplurality of condenser pipes.
 8. A Stirling refrigerating systemcomprising: a Stirling refrigerating device including a piston and adisplacer that reciprocate with a predetermined phase difference kepttherebetween inside a cylinder having a working medium sealed therein, aheat absorber that absorbs heat from outside to produce cold as a resultof the working medium being expanded in an expansion space formed insidethe cylinder as the displacer reciprocates, and a heat rejecter formedas a ring-shaped refrigerant flow passage that rejects, to arefrigerant, heat generated as a result of the working medium beingcompressed in a compression space formed inside the cylinder as thepiston reciprocates; a heat-rejecting heat exchanger disposed around theStirling refrigerating device with a gap secured in between and formedso as to have a refrigerant flow passage; a refrigerant circulationpassage formed by connecting the refrigerant flow passage of the heatrejecter and the refrigerant flow passage of the heat-rejecting heatexchanger with a pipe; and circulating means for circulating arefrigerant through the refrigerant circulation passage.
 9. A coolingapparatus having a Stirling refrigerating system as claimed in one ofclaims 1 to 8 housed inside a machine compartment formed at a bottom ofa body of the cooling apparatus, wherein an interior of the body isenclosed with a heat-insulating material and is cooled by exploitingcold generated in the heat absorber as the Stirling refrigerating deviceis operated.